Data transfer system



April 11, 1961 E. ESTREMS 2,979,260

DATA TRANSFER SYSTEM Filed Sept. 21, 1956 12 Sheets-Sheet 1 FIG. 10

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EUGENI ESTREMS BY gm AGENT April 1951 E. ESTREMS 2,979,260

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April 11, 1961 E. ESTREMS 2,979,260

DATA TRANSFER SYSTEM Filed Sept. 21, 1956 12 Sheets-Sheet 12 naL1ielal +|xlllalalhlxl D [1 2 3 411 2 3 M1 2 3 M1 2 3 MM]. 2 3 H1 2 3 M1 2 3 M1 2 3 m s'rll 2 us 6 napl1 2 3 1 ss'rsb-c TRANSFERI- TRANSFER'.- AGL 1 I 2 PROGRAM I CHANGE FIG. I6b

United States Patent DATA TRANSFER SYSTEM Eugeni Estrems, Saint Mande, France, assignor to International Business Machines Corporation, New York, 1 N,Y., a corporation of New York Filed Sept. 21, 1956, Ser. No. 611,272

Claims. (Cl. 235159) This invention relates to a data transfer system for use in a high-speed computer, and particularly to electronic circuits for automatically controlling successive transfer and shifting operations in such a computer that is capable of performing division and multiplication operations.

A major problem in high-speed computer construction is that of overcoming delays in the transfer and shifting of data between the various storage and adding circuits, particularly during multiplication and division operations. Associated with the problem of constructing ever faster computers and data processing systems is that of developing efiicient and simple circuits that reduce'the time for performing the arithmetic operations. It has been found that computers which operate in a serial manner reduce the number of circuits needed to perform successive transfers particularly in the case of multiplication. The serialtype computer may be generally identified by the simultaneous processing of the digits of two quantities by the same adding device in accordance with a particular se-' quence. However, special control devices have been required in order to set up and change'these sequences automatically. For example, in the case of multiplication proper sequencing requires that the digit of a certain order in the partial product is made to correspond to the digit of the same order in the multiplicand. Thus after the digit of p order in the unit partial product has been made to correspond to the digit of the same order in the multiplicand, it is then necessary to make the digit of the p+1 order in the partial product correspond to the digit of the p order in the multiplicand. This is generally accomplished by directing the multiplicandinto a delay line so that after the first operation, the unit digit is in the position formerly occupied by the tens digit. It is obvious that such a method reduces computer speed, since it requires the employment of delay circuits or lines. i

Another method for controlling the sequential emission of order digits is that of thepulse distribution chains. However, the pulse distribution chains that are now employed also fail to develop automatically and without loss of time the desired sequencing, for example, between Another object of the invention is to. provide improved pulse. distributing chains associated with two registers in which the number of pulses emitted by said chains is digit orders in the multiplicand and those inthe partial products. V Therefore, the principal object of this invention is to provide an improved means foraccomplishing the proper sequencing or transfer of digits during computer operations, particularly multiplication and division.

Another object of the invention is to provide an improved data transfer system in the form of flexibly con-' trolled 'pulse distribution chains whose function is to arrange and accelerate transfer of digits between the registers and to reduce loss of time between successive transfers. e 1' I i I A i Another object of the invention is to provide 'anjim proved data transfer system for multiplication and division operations inwhich cycles ofmulti'plicationby determined by one of said registers.

Another object of the invention is to provide flexibly operating pulse distribution chains in which any element of the chain may be operated to repeat any determined number of pulses and in which the chain elements. may be skipped in order to reduce the final number of pulses emitted by the pulse distribution chain during any operation cycle.

'Other objects of the invention will be pointed out in' the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated, of applying the principle. 7

In thedrawings: I Figs. 1a and 1b illustrate a block diagram of the principal computer elements.

, Fig. 2 illustrates a time chart of the main control the computer of Figs. 1a and 1b.

Fig. 3 illustrates a schematic of a double outputinverter.

' Fig. Fig. lower.

Fig. 4a is a block diagram of. Fig. 4. Fig. 5 is a schematic diagram of a conventional single output inverter.

Fig. 5a is a block diagram of Fig. 5 Fig. 6 illustrates a conventional AND circuit.

Fig. 6a illustrates a block diagram of Fig. 6. Fig. 7 illustrates a conventional 0R circuit, Fig. 7a illustrates a block diagram of Fig. 7.

Fig. 8 illustrates apulse distribution chain which serves as a primary or digit ring. a

.Fig. 9 illustrates a pulse distribution chain which serves to' control the operation of the storage circuit. Fig. 10 illustrates a pulse distribution chain which conpulses that 3a is a block diagram of Fig. 3.

4 is a schematic of a conventional method fol:

trols the operationof the accumulator.

Fig. 11 illustrates the circuits that control the control the'accumu- Fig. 15 illustrates a pulse timing diagram of transfer operations during a particular multiplication.

Figs. 16a and 16b illustrate a ation-. v I

General description Figs. la and 1b illustrate the interrelationship between. the various 'circuit's constituting the invention" andQcOnK ventional circuits forming a high speed computing sys te "application Serial No. 544,520 in =thenarn'e 'of fiarhiltioin et-a1, filed on November 2, 1955.

In Figs. 1 a and 1b-- the storage .unitfdqcontains the Patented Apr. 1 1, 196 1;

pulse timing diagram, of transfer operations during a particular division oper- .tive) or complementary (line 74 positive).

divisor or multiplicand and the accumulator 50 contains the dividend or multiplier. Transfer of digits on line 51 from the storage unit to adder 49 is controlled by switch 53. Digits are delivered from accumulator 50 to adder 49 on line 52. Transfer from the accumulator 50 to storage unit 44 is controlled by a conventional switch 205. The output of later 50. p I

Digit selection in storage unit 44 is accomplished by a pulse distribution chain (Fig. 9) comprising a five pulse chain group 42 and a three pulse chain group 43. Both chain groups are capable of being operated together to form a single eight pulse chain.

Whether the chain of Fig. 9 reads out three, five or eight digits from a particular location of storage unit 44 will be determined by a positive pulse on terminal 126, 124 or 125 respectively. The storage ring of Fig. 9 is reset by a positive pulse on line DGX4 from the primary ring of Fig. 8.

Digit selection in accumulator 50 is under the control. of the pulse distribution chain of Fig. 10. This chain consists of two pulse chain groups 59 and 60, the former being identified as chain group agl-agx andthe' latter as chain group a1-a4. Operation of both chain groups is initiated by the circuits of Fig. 12 and maintained in. operation by the pulses on lines AP, BP and NR provided by a conventional pulse generator 206. The simultaneous operation of the chain groups develops double pulse groups that operate, for example, diiferent twodiode type coincidence circuits to produce sequential. pulses for reading out digits from the accumulator 50.. Such a coincidence type connection may be seen in Fig. 8.

The circuits of Fig. 13, reference 61 in Fig. 1b, control the starting of accumulator operation in accordance with signals received at input terminals 62. However, the signals are permitted to initiate the accumulator ring only when the primary ring of Fig. 8 delivers a positive pulse on line DGX4 during the initial period of computer operation when the circuits are being set up. At such. time line T is assumed to be UP.

Carry'control and suppression are provided by Fig. 11 (reference 58 in Fig. 1b). Such suppression occurs automatically during multiplication when positive pulses arrive on lines D3 and D63 from the primary chain of Fig. 8 or when a positive pulse occurs on line D632, as will be subsequently described in detail. I

The circuits of Fig. 12 (reference 55 in Fig. 1a) provide-control of readout from storage unit 44, and determine whether such readout shall be true (line 73 posi- The truecomplementary circuit, controlled by pulses on lines 73 and 74, may take the form described in US. Patent No. 2,624,508. Line 56 controls the entry of a zeropulse into adder 49, and line 57 controls the entry of a nine pulse. 'Line 138 controls readout from storage unit 44 in accordance with pulses received from the primary ring of Fig. 8 and the storage ring of Fig. 9. f

. Thecircuitsof Fig. 14 (reference 63 in Fig. la) control the division and multiplication operations of the computingsystem'in accordance with pulses received at input hubs 64 (multiplication) and 65 (division). The signals developed by the circuits of Fig. 14 serve to control the operation of all the other transfer and shift circuits of Figs. 1a and lb except the storage ring of Fig. 9. Thecircuits of Figz'14 also sense the end of divisionand multiplication, providing positive pulses on lines 166 and 218 which maybe usedto commence the next operation cycle. v

V Ultimate control and synchronization of the shift and transfer operation in the disclosedcomputing system is provided by the pulse distribution chain of Fig. 8 comprising the d1--d4 chain group and. the dgx-dg4'chain tive pulse on line 16 and stepped along by the negative pulse on line NR. In accordance with input conditions,

adder 49 is transferred to accumu-' group. The primary ring of Fig. 8 is started by a posithis chain may develop any number of control pulses.- The primary ring of Fig. 8 may be termed the master ring, and the storage ring of Fig. 9 and the accumulator ring of Fig. 10 may be termed the slave rings. The pulse developed by the primary ring on line DGX4 resets the storage and accumulator rings.

Basic circuits The basic circuits are conventional in nature, and there-- fore only a brief statement is given in explanation of them.

The first of these basic circuits is illustrated in Figs. 3' and 3a, with the latter merely being a block diagram of the former. The double output inverter of Fig. 3 comprises a duo-triode, the left hand grid of which is connected through a resistor to input terminal 2. When the double inverter is operated from the left side by the application of a positive voltage at input terminal 2, output terminal 3 goes down in potential due to the flow of current through the plate resistors connected to thepositive line. At the same time output terminals 4 and 5 have an increased potential because the right-hand triode of the duo-triode combination is not conducting at this time. The reduced potential at the left-hand plate is transmitted through a resistor-capacitor network to the right-hand grid, thereby preventing the right-hand triode from conducting.

The application of a negative pulse at input terminal 2, has the reverse effect on this inverter, since it makes the left-hand triode non-conductive and the right-hand triode conductive. Similarly, the application of a positive potential at input terminal 6 or 7 makes the right-hand triode conductive and the left-hand triode non-conductive as explained. It is thus possible to control the output condition of this inverter by the application of suit-- able input voltages at more than one input terminal. in the block diagram of Fig. 3a the input terminals are illustrated in the lower area and the output terminals in the upper area. These terminals will assume their re spective relation when the block diagram of the double inverter is shown and described throughout the succeeding clrcults.

Figs. 4 and 4a illustrate a convertional cathode follower. As shown in Fig. 4, a positive potential applied at input terminal 11 makes the triode conductive and current to flow in the cathode resistor, in this way developing a positive potential at output terminal 12. Fig. 4a illustrates the same circuit in block form, and the relative positions of input terminal 11 and output terminal 12 will remain the same whenever the cathode follower block diagram is shown in succeeding circuits.

Figs. 5 and 5a illustrate a' conventional single output inverter. In Fig. 5 a positive pulse applied at either input terminal 233 or input terminal 234 makes the triode conductive causing current to fiow through the plate resistor and developing thereby a reduced potential at output terminal 232. Similarly an absence of a positive voltage .at either input terminal will'not make the tube conductive .that they will maintain whenever this inverter block diagram-is employed in succeeding circuits.

initiates or When the: transfer of digits between storage unit 44 and accumu-- enraged I- igs. 6 and 6 a illustrate a conventional AND circuit which operates in a manner to develop an increased potential at output terminal 13 whenever positive voltages are applied simultaneously at input terrrnnals 14 and 1:.

The circuit of Fig. 6 will be'illustrated as shown in Fig. 6a whenever an AND circuit is shown in the succeeding circuits. I

Figs. 7 and 7a illustrate a conventional OR circu t. The application of a positive potential at e1ther'or both input terminals 29 or 30 will bring about an increased potential-at output terminal 28. Fig. 7a is employed to illustrate the two-inputOR circuits of Fig. 7 in succeeding circuit diagrams. v v The -traiisfer-and shift circuits The -bas iccompcnents'of Figs. 3-7 are shown interconnected in Fig.'8to form a pulse distribution chain'h'aving tWo pulse developing groups. One such group is composed of four latch circuits d1, "d2, H3 and d4. The other group is made up of five latch circuits dgx, dgl, dgZ,

dg3 and dg4. Each latch circuit in the two pulse developing groups is composed of a double position inverter (Fig. 3), cathode follower (Fig. 4) and an AND circuit (Fig. 6). In the initial pre-operating condition the 'left triode of each double inverter is non-conductive and the right triode is conductive.

Referring to latch all, a positive pulse (for example, 40 volts) applied to line 16 is gated by a diode to input terminal 2 of the double inverter (Fig. 3) which causes said inverter to develop a positive potential at its output terminal 5. This developed potential then operates cathode follower 10 and makes a positive potential available to the right diode of AND circuit 17. If at this time a positive potential is present on line D, AND circuit 17 delivers a positive signal through a diode to input terminal 2. So long as a positive voltage of sufiicient magnitude is present on line D, latch 111 will form a closed loop and a positive signal will be available on output lme 'Dl. Of course, when no positive voltage is applied originahy on line 16, the latch in stage d1 will not be developed inasmuch as output terminal is negative at this time. In the subsequent discussion each conductive line or terminal will be said to be UP when a positive potential exists, and DOWN when a negative potential exists.

At the time that latch d1 is energized, output terminal 4 .of inverter 1' (Fig. 3) is also in the UP condition, there by applying a positive potential to input terminal 6 of the double inverter 18. This positive voltage makes the right triode of the double inverter 18 conductive thereby preventing cathode. follower 19 from, being .conductive an'd'latc'h d2 from being energized. Thus a pulse cannot be developed on output line D2 at this time. Output latches d3 and. d4 also cannot develop an'output pulse at this time., In the case of latch d3 the positive potential .rriade available to the right inverter by the inoperative condition of the left inverter maintains the right inverter in a state of conduction regardless of the DOWN condi tion of output terminal 4 of double inverter 18 inlatch I To bring; about the energization of the next succeeding stage orlatch it is only necessary to develop a negative pulse on line D. Assuming that latch d1 is in an energized condition, the application of a negative pulse on line D causes input terminal} of the double inverter 1 to go DOWN and output terminal 4 to go DOWN also.

.The negative swing of terminal 4 makes input terminal 6 of two-position inverter 18 of latch d2 sufficiently negative, thereby causing a positivepulse to be apphed to cathode follower 19. '-The positive pulse developed by cathode follower 19 is sent to AND circuit 20, which'also receives a positive-pulse from line D-at this time. Thus *stage d2. is energized, and a positive pulse is made available for succeeding circuits on line D2.

Latches d3 and d4 are operated sequentially in response tofne'ga'tive voltages developed on 'controbline D, in a mann'er similar to that'alr'eady described with regard that of control line D described above. veloped by the pulse generating group dgxQdgI dg tare delivered to various circuits of the computer andto the input circuits of the pulse distributing chain of Fig. 8.x

'to latches d1 and d2. However, latches J3 and '34 also develop output signals that serve to control the "operation of the pulsedeveloping group dgx, agl, dg2, dg3 and a'g4.

Latches cigx, a'g1-dg4 are identical in operation and structure to latches dl-dft. As in the case ofrlatch d1 latch dgx is also initially energized by'the application of a positive potential on line 16. This voltage is delivered through a diode to the input terminal of the double inverter 33 which operates in the manner already described with regard to inverter 1 of latch d1. Once latch dgx is energized, the stepping of the pulse group formed by this latch and latches dgl-dg4 is controlled by the negative pulse developed on line DG in a manner similar to The pulses de- It has been statedthat the operation of the two pulse dist'rbuting groups dl-d4 and dg'x, dg1dg4'is controlled 'by the negative potential applied at input terminals'D and DG respectively. In the case of pulse distributing group d1d4, this means thatthe latches are operated sequentially whenever cathode follower 35 is non-conductive. This condition occurs Whenever OR circuit34 has not been made operative by a positive pulse developed on line 36 by the latch circuit composing double inverter 39, cathode follower 40 and input OR circuit 54. This latch circuit may be energized in a number of ways. A positive pulse received on line 71 or 72 from the circuits trol latch may be tie-energized by a positive pulse on line AP, which pulse is inverted and applied to terminal 4 of double inverter 39. Cathode follower 40 is made inoperative, and the negative pulse on lineNR brings control line D DOWN to step along the pulse group A similar input control system is provided for pulse distributing group agx, dgl-dg4. Control linefDG is DOWN whenever cathode follower 32 is caused to be nonconductive by the absence-of a positive pulse atthe input of cathode follower 41. when the latch, comprising double inverter 26, cathode follower '25 and OR circuit 27, is in its de-energized con dition. The DG control latch is identical to the D- control latch. V p t This latch may be energized in a number of different ways. An AP signal made available at the upper inputz' terminal of OR circuit 27 will energize the DG control latch. The latch-may be die-energized through the'operation of inverter 24. Operation of OR circuit 2 3 is controlled by AND circuits 38 and 22 For operating AND.

circuit 38, it is necessary that positive pulses be applied simultaneously on line D64 from latch dg4, line D3 from 7 latch (13, line 68a from Fig. 14, line73d from Fig. 12

and a positive pulse on line BP. AND circuit 22'can only be operated when positive pulses are applied-simuL 7 taneously on lines D4- andBP. The sequence and, rela tive time orders in-which these two input control circuits are operated for-controlling the operation of the two pulse distributing groups will be discussed subsequently,

, when the logic of the data transfer system is taken up in greater detail. It is sufhcient to state at thistime that the pulse distributinglchain of Fig. 8 is capable or devele oping twenty pulses during any..operation"cycle or.an-,.- other number of pulses in accordance with: computer The latter condition occurs" conditions. Reference to Fig. 8 will show additional circuits for developing pulses at other than the regular time intervals. For example, in the left bottom corner of Fig. 8 is shown AND circuit 132 and cathode follower 135 which operate to develop a positive pulse on line DGX4 1 only when positive pulses are developed simultaneously by latch d4 and latch dgx. Similarly, AND circuit 133 and cathode follower 136 develop a positive pulse on line DG32 whenever latches d2 and dg3 develop positive pulses simultaneously This also applies to AND circuit 134 and cathode follower 137 which develop a positive pulse on line DG11 whenever latches d1 and dgl are operating simultaneously.

It should be understood that references such as DGX4, DG32 and D611 are intended'to indicate a particular conductive line and also the relative time interval in which a positive pulse appears on said line. That is to say, .DGX4 indicates that both a D4 pulse and a DGX pulse have joined together to form the DGX4 pulse. Similarly the reference D632 indicates that the DG3 pulse and the D2 pulse form the D632 pulse. This identification of pulses should be clearly understood inasmuch as it is found in the description of the logic that follows.

The two pulse generating groups are initially operated simultaneously since the positive pulse on input line 16 is fed simultaneously to double inverter 1 and 33. In the original reset condition, latches d1 and dgx are energized to develop separate pulses on lines D1 and DGX at what may be considered to be time interval DGXl. Thereafter, the upper and lower chain groups are stepped along by negative pulses on line NR.

For example, the first negative NR pulse after reset tie-energizes latch dl and energizes latch d2. Latch dgx is not de-energized because negative signal NR is not permitted to go through OR circuit 31 except when the' upper chain group reaches stage d4 or the stages d3 and d4 are energized simultaneously. Therefore, at'this time interval, that is DGX2, output lines DGX and D2 are UP. The lower chain will continue to develop a positive pulse on line DGX until the upper chain group reaches stage d4, at which time OR circuit 31 will allow negative pulse NR to de-energize latch dgx and energize latch dgl. I

Both chain groups are capable of automatically resetting themselves after their last stages d4 and dg4 have been energized, unless of course the conditions in the computer require that a greater or lesser number of points than 20 be developed for a particular operating cycle.

Assume that it is desired to reduce the number of pulses developed by the primary chain of Fig. 8, and the desired number is ,17, as shown below.

DG: 1 2 3 4 :X D 2123421234112341123424 The sequence continues normally until time'interval DG44, after the 16th pulse. The pulse counting is said to begin at time interval D611 and to end at time interval DGX4. At time interval D644, AND circuit 37 isoperated, energizing the upper group control latch, comprising OR circuit 54, inverter 39 and cathode follower 4%). This prevents the upper chain from being stepped along from stage (14 to stage (11. However, the lower chain is permitted to be stepped along from stage dg to dgx. Thus pulses DGXl, DGXZ and DGX3 are suppressed, and only 17 pulses are counted.

The primary chain may be reduced to 16 pulses as follows:

130: 1 2 a 4 X 1 D :1234zl234zl234zl23z421234 At the end of time interval D643 or the th pulse, AND circuit 38 is operated to de-energize the lower group control latch, comprising OR circuit 27, inverter .26 and cathode follower 25, thereby permitting the nega- -tive NR pulse to step the lower group from stage dg4 to dgx. Since the upper group is not disturbed at this time, it moves normally from stage d3 to stage d4.

It must be understood that other similar input control circuits may be employed to reduce the primary chart of Fig. 8 to any number of pulses.

Similarly, the primary chain may have the number of its pulses increased any amount. This is accomplished ,by maintaining the upper chain group in a selected position for any length of time. In such a case it is necessary to maintain the upper group control latch in an energized condition for a sufficiently long time interval. A continuing positive pulse on either input line 71 or 72 can maintain this latch energized indefinitely. Assuming that either input line 71 or 72 is caused to be UP at time interval DG32, the primary chain of Fig. 8 will continue developing dg32 pulses until that input line goes DOWN, at which time the upper and lower chains will continue their normal operation.

Reference to Fig. 2 will illustrate the primary pulses which'were discussed with regard to Fig.8. Each of the pulse identifications, for example, AP, BP, NR, etc. will 'be shown in the described circuits beside the conductive line which carries the pulse. In other words and referring specifically to Fig. 8, pulse AP is shown adjacent the line that feeds OR circuit 27, pulse BP is shown adjacent the line that feeds AND circuit 22, etc. A single pulse is shown simply because only one such pulse is necessary to initiate the operation of the primary chain after which control of the operation of this chain is assumed by the input control circuits. Fig. 2 illustrates the relative timing and relationship of the primary pulses. The pulses AP, BP, NR and 16 are developed by any conventional pulse generating device 206 (Fig. 1b). Pulses d1-d4 are developed by the upper pulse distributing group of Fig. 8.

Fig. 9 illustrates the storage ring which comprises eight latches stl-stS that are similar to the latches discussed with regard to Fig. 8. However, in the latch of Fig. 9 two cathode followers are connected in parallel between the output of each double inverter and its input AND circuit. The storage ring is actually an open ring which is composed of a ring of five and a ring of three, the two of which may be operated together to form a ring of eight.

The operation of the storage ring of Fig. 9 is initiated or reset by the presence of a coincidence at AND circuit 119. This occurs when input lines NR, DGX4, and either input terminal 124 or are UP. In such a situation, AND circuit 19 is conductive and the input of inverter 120 is UP. This causes the input of inverter 121 to be DOWN and input terminal 3 of inverter 122 to be UP. Reference to Fig. 3 shows that when input terminal 3 is UP, the left triode is made conductive, thereby causing output terminals 4 and 5 of inverter 122 to be UP. With output terminal 5 of inverter 122 in the UP condition, the two cathode followers in stage st1 are made conductive and develop a positive pulse on output line ST1. Simultaneously, a positive pulse is delivered to the right diode of the input AND circuit in stage stl. So long as line NR is UP, the input AND circuit develops an UP condition at the control grid of the left triode of inverter 122, maintaining stage STl in a closed loop. All other stages of the storage ring are inoperative at thistime. Each succeeding negative signal on line NR causesthe ring to be stepped along in a manner already explained with regard to Fig. 8.

It has been stated that the storage ring of Fig. 9 is capable of developing groups of three pulses, five pulses, or eight pulses. The three pulse chain is developed by the presence of a positive pulse at input terminal 126 at the same time that a positive pulse occurs on line DGX4 from the primary ring of Fig. 8. These simultaneous pulses operate AND circuit 131 and through an OR circuit make inverter 127 conductive and inverter 129 nonconductive. Input terminal 3 of inverter 130 is therefore caused to be UP and operation ofthe three pulse chain mostdio'de of OR circuit 112.-

ST6-ST8-is initiated. Subsequent entryo'f negative pulses on line NR steps this chain along sothat the'output pulses are successively developed at outputt erminals T6, ST7

inverter 122 of stage ST1 initiates the five pulse chain STIASTS. In the manner previously explained successive entries of negative pulses on line NR, steps the chain along to provide positive pulses at output terminals STI- ST5. At the end of the fifth pulse, the chain is stopped and is revived by the simultaneous application of positive voltages at the input of AND circuit 119. w

The eight pulse chain includes the three and live pulse chains mentioned above. This chain is initiated as stated above in the case of the 5 pulse chain ST1-ST5 with'the exception that a positive voltage is impressed at input terminal 125 rather than at input terminal 124. This voltage permits AND circuit 119 to be operated for the purpose of starting chain operation. Upon the operation of stage STS a positive voltage developed by this stage is delivered to the AND circuit 123 at the same time that a positive voltage is made available to this AND circuit from input terminal 125. Operation of AND circuit 123 provides a positive voltage through an OR circuit to inverter 127 for the purpose of continuing the count through the three stages ST6ST8.

Fig. illustrates an accumulator ring having two pulse chain groups that are similar'to the pulse chain groups discussed in the case of Fig. 8. The upper group a1-a4 and the lower group agl-agx are initiated by positive voltages applied at two of the input lines from the control.

circuit of Fig. 13. Assuming that a positive voltage is applied on line a1, inverter'90 operates in a manner to drive cathode follower 88 into a state of conduction developing a positive pulse on output line A1 and operating AND circuit 89 in conjunction with thepositive voltage on control line 87. .Once initiated the chainis then stepped along'by negative pulses appliedon line NR through OR circuit 85 and cathode follower 86 to line 87. M5

The advance of pulse group al-a4 may be-stopped by the development of a positive pulse by AND circuit 94 when stages A4 and AG4 in Fig. 10, as wella's line BP,

deliver positive voltages. The UP condition at the input of AND circuit 94 is transmitted through an'OR circuit tothe input of inverter 100, which drives cathode follower 101 into a state of conduction, and causes line 102 to be UP also. This condition isjreflected in. line '87 which prevents negative pulses availableron line N-R to step the chain along. Generally the negative voltageon line" NR is permited to'step along chain a1-a4 because line,

102 is DOWN. The positive'voltage on line AP is converted into a. negative condition'at the input of cathode follower 101 through an inverter. With a DOWN condition at the input of the bottorndiode of ORcircuit 85, the negative pulse available on line NR is permitted to be delivered to line 87 for the purpose of stepping chain group a1-a4.

Chain group a1-a4 is resetby the presence simultaneously of two positive signals at the input of AND circuit 113. The upper diode of AND circuit 113 is controlled byvoltages provided by OR circuit 112, which is operative whenever stages .agl, 'ag2 or' ag2 develop a positive pulse or when positive'voltages exist on lines 670 and AGX simultaneously. In the latter case, AND circuit 105is operated making cathode follower; 107 conductive and developing a" positive voltage on the lower.

7 The lower diode of AND-circuit113 is positivewhet:-

duc'tive. This occurs wheneverline AP In fa case, the outp'ut of double'inverter' 97 is also UP'arid line"-96 of the latchcirc'uit, which the inverter 97 fornis "followers 99, making-the'latter conductive. inputs of AND circuit 113 UP, the output of inverter a part,-is also UP. The positive voltage on line 96 is delivered by'OR circuit 98 to the control grids of cathode With both 114'is DOWN and the output of inverter 115 is UP.

This has the etfect of resetting chain a1-a4.

Lower chain group agl-agx is initiated or reset by a positive pulse provided at input terminal 3 of inverter 11 1 of stage ag1. The lower chain group is initially 'starte'dby a positive pulse on input line agl from the circuitof Fig. 13. Upon completion of the first full cuit 95. With the output of AND circuit '95 UP, the.

cycle of operation a positive pulse is developed on line A4 which together with a BP pulse operates AND cirout put; of the succeeding-inverter is therefore DOWN and'line' '96 is also DOWN. This permits the negative pulse on line NR tobe delivered through OR circuit 98 and cathode followers 99 to'the control line of group a'gl agx forthe purpose of moving the chain along.

The-upper and lowerchain groups of Fig. 10 may be started in any sequence since all the stages are independently controlled by pulses provided by the circuit of Fig.

13, "Howeveran upper stage is operated simultaneously -withalower stage, as in the case of the primary ring of Fig. 8.

'a1a4 produces positive pulses sequentially on its output Stage agl will continue to produce a positive pulse on its output line AG1 during the time that chain group lines a-1- a4. However, when stage a4 develops an output pulse on its output line a4, AND circuit 95 is operated for the purpose of permitting the negative pulse on line NR to 'step'the lower chain group to stage ag2. It should be noted that'group a1a4 is stopped whenever stage ag4 develops apositive pulse because an zzg4 pulse is not deliveredto OR' circuit 112butinstead ismade available to line'102 go UP to prevent the negativepulses on line in the manner shown in Fig: 8 before operating the digit 1 order pentodes primed 'bythe storage triggers in ,eacfh' order'of the accumulator. ,It will -be noted that other pulse's'd'eveloped by the accumulator ring serve'to c'ont rol'the circuits of Fig"s.fl12 and l4. I I 1 i Fig. -lj1ill-us tr ates the circuits which develop carryand computing'system illustrated n" A s'sign'ed reference numeral 5 8 f in, j

AND 'circuit 94. The presence of positive pulses on lines-A64, A4 and "BP at the input of circuit 94 makes NRfrom reaching line 87 for the purpose of stepping along chain A1-A4 at the time the lower chain is in stage AGX.

The ability of stage ag4 to prevent the stepping along of the upper chain group at the time that stage A4 of the upper group is energized enables the accumulator ring of Fig. -10 to' develop a 17 point operation cycle in accordance-with the following tabulation:

AG: 1 2 3 4 X -After'the positive pulse on line A4 and the positive pulse on line BP operate AND circuit 95 for the purpose of allowingthe -negati ve'pulse on line NR to step the lower ..-'group'from stage-ag3 to ag4, the positive pulse developed V by stageag4 preventsa4 of the upper group from returning .to stage a1. Line A4 remains UP at 'the'time line AG4is brought UP to operate 'AND circuit 94 and ther e upon xprevent negative pulse NR fromresetting the upper chain group. Resetting -is accomplished at time interval The chain of 17 pulses which the accumulator ring of .Fig. :10 is capable of-producing controls the readin' and readout of 1'7 digits into'and'out of accumulator 50 (Fig. lb). It is-understoo d that pairs of. said A'sand AG pulses are gatedthrough individual coincidence circuits "m ni est ever parallel connecting cathode followers 99 JQ'IB'CO'IL-JWEZJFES. Iaand 1b,and fa about a DOWN condition at the output of inverter 210 and an UP condition at the output of inverter 211. This results in the operation of double inverter 212 and cathode follower 208, which forms a part of the carry control latch, and causes output line C2 to be UP. The positive signal on line C2 designates a carry for adder 49 in Fig. 1a.

In the case where there is an absence of a carry in adder 49 of Fig. 1a, input line NC1 is UP, and if line BP is UP simultaneously, AND circuit 215 is operated. When the output of AND circuit 215 is UP, the output of inverter 216 is DOWN and the output of inverter 5 217 is UP.

The no carry control latch, comprising double inverter 213 and cathode follower 214, is operated in a manner to cause output line NC2 to be UP. This latch is maintained energized by the positive potential on line NR.

Suppression of a carry signal received on line C1 from adder 49 is accomplished at two different time intervals. For example, it is desirable to suppress the carry at the time of the addition of a digit 9 and an order digit of accumulator 50 when the multiplier is reduced by 1. In

such a case, AND circuit 167 is operated by positive pulses on lines D3, DG3 and 66A. With the output of AND circuit 167 UP, the output of cathode follower 197 is also UP causing the output of inverter 207 to go DOWN.

Cathode follower 208 then reflects the DOWN condition on output line C2, thereby conveying to adder 49 of Fig.

1a the information that the carry is suppressed.

Similarly, the carry is suppressed whenever the transfer of a true value of the number in storage unit 44 to adder 49 is stopped. Such suppression occurs at the time intervals at which a positive pulse is formed on line DG32. The presence of this pulse at the same time that input lines 67D and 73A are UP, operates AND circuit 196 which makes cathode follower 197 conductive. As

explained above, the operation of cathode follower 197 brings about a negative or DOWN condition on output line C2. I

The operation of cathode follower 197 by either AND circuit 167 or 196 also energizes the no carry latch, comprising double inverter 213 and cathode follower 214,

lower 197 is operated, the cathode follower will have no, o effect on the second latch because the positive pulse on line NCI will have operated the second latch.

The storage control circuits of Fig. 12 serve to control the reading of data in storage unit 44 (Fig. 1a) and to accomplish the emission of zeros and nines during various,

arithmetic operations in the computing system ofFigs. la and 1b. The pulse developed at output terminal 138 accomplishes the readout of data recorded in storage 44.

For example, the presence of a positive condition on either of the lines NR, AGX and ST8 brings about the, 0

operation of OR circuit 225. Similarly, when lines STS and 124A are UP simultaneously, AND circuit 227 is caused to go UP for operating OR circuit 225. In any one of these four input conditions the output of inverter 224 is DOWN and the output of inverter 226 is UP to. 55 drive cathode follower 186. With input line AP UP at this time, AND circuit 187 is operated to drive parallel connected cathode followers 189 into conductivity, thereby causing output terminal 138 to goUP.

Output line 138 may be brought UP for the purpose of reading data in storage unit 44 when inverter 185 is i .not operated by preceding control circuits, For example, when input lines DG11 and 67B are UP simultaneously,

AND circuit 1821is operated causing a'positivepulse to be delivered through an OR circuit to inverter 183. The; 15 way.

negative potential at the output of inverter'183 is delivered through cathode follower 184 to the input of inverter 185. This causes the output of inverter 185 to go UP, thereby operating cathode follower 186 for the purpose of developing a positive voltage at output terminal 138. It should be noted that the operation of cathode follower 186 energizes a latch through an OR circuit, in-

verter 183, cathode follower 184 and inverter 185. So long as this latch is energized, output terminal 138 will be brought UP in accordance with the positive pulses impressed on input line AP (see Fig. 2).

Output terminal 138 may also be brought UP by a positive voltage developed by the circuit of Fig. 13 on line 181. As in the case of AND circuit 182 previously explained, the voltage on line 181 is delivered through an OR circuit to inverter 183 thereby initiating a latch of which inverter 183 forms a part and thus bringing about a positive condition at output terminal 138.

1 Output terminals 73 and 74 of the storage control cir- 20 cuit in Fig. 12 operate switch 53 in Fig. 1a and the circuits of Figs. 8, l1 and 14 for the purpose of controlling the transmission of data from storage 44 to adder 49. When output terminal 73 is UP, the true value of the data stored is transferred from storage unit 44 to adder 49. When output terminal 74 is UP, the complement value of the data in storage unit 44 is transferred to adder 49.

Output terminal 73 is in an UP condition whenever the latch, represented by double inverter 142 and cathode follower 143, is energized. This occurs whenever OR circuit 152 is operated by either AND circuit or AND circuit 195. In the case of AND circuit 140, its operation is controlled by the presence simultaneously of positive voltages on input lines DG11, 66B and NT. On the other hand, AND circuit 195 is operated by the presence simultaneously of positive voltages on input lines DG11 and 69. When the output of AND circuit 152 is UP,

double inverter 142 drives cathode follower 143 into a state of conductivity, causing its output to go UP for setting UP the latch and accomplishing the transmission of the selected true data from storage unit 44 to adder 49.

' pulses on its lines DG11, DG32 or DGX4.

During the first time interval of operation of the primary chain of Fig. 8, a positive signal is developed on output line DG11 which, in conjunction with the positive signals available on lines 70 and 68B, operates AND circuit 178 and through an OR circuit makes inverter 179 conductive. Cathode follower 180, therefore, cannot be operated and the upper diode of OR circuit delivers the negative voltage to inverter 146, whose positive output then drives cathode follower 47 to. cause output terminal 74 to go UP.

gized at time interval DG32 or DGX4 of each operating cycle. -At time DG32 the positive pulses on input lines DG32 and 67B operate AND circuit 144, OR circuit 145 and inverter 146, making cathode follower 47 non-conductive and. pulling line 74 DOWN. At time interval DGX4 a positive pulse is fed by the primary chain of Fig. 8 to OR circuit- 145 to bring output line 74 DOWN in the amass During multiplication complements transfer is not require'd,an'd output line 74 is always DOWN. The absence'of a division indicating pulseon line 6813 prevents coincidence at AND circuit .178 and maintains the succeeding complements transfer latch de-energized.

The positive pulse on line DGX4 which causes output line 74 to go DOWN, in the manner explained, also operates inverter 141 in order to de-energize the latch represented by double inverter 142 and cathode follower 143., This has the effect of bringing. output terminal 73 DOWN at the end of an operating cycle. The true transfercontrollatch, comprising double inverter 142 and cathode follower 143, is energized wheninputline 69, indicating, a no carry condition'in adder 49, is UP or when the first pulse DG11 arrives from the primary chain during a multiplication operation.

Output terminals 56 and 57 control the emission of Zero value pulses and nine value pulses respectively to adder 49. When these output lines are UP, switch 53 in Fig. 1a is directed to pass zero and nine pulses, as the case may be to adder 49, but when they are DOWN such passage is not permitted. v

In terms of the circuit of Fig. 12, output terminal 56 is UP only when cathode follower 150 is operated. This occurs when all three input lines of OR circuit 148 are DOWN and the output of inverter 149 is thereby in an UP condition. However, when one of the lines 159, 74a and the line from cathode follower 223 is UP, output terminal'56 is DOWN and the transmission of zero pulses is barred.

It has been stated under what conditions output terminal 74 is caused to be UP. When output terminal 74 is brought UP, its associatedline 74a delivers apositive pulse to OR circuit 148 for the purpose of barringthe trolled by cathode follower 223. When cathode follower 223 produces a positive pulse that is fed to OR circuits 148 and 219, the latter OR circuit will operate inverter 220 to cause cathode follower 221 to be non-conductive and output terminal 57 to be DOWN. The operation of OR circuit 148 has the same contact on inverter 149 and cathode follower 15.0'to bring output terminal 56 DOW-N. However when cathode follower 223 is not conducting, the output lines 56 and 57 will always be in opposite states.

Cathode follower 223' on input line 181or positivevoltages occur simultaneously on input lines DG11 and 67b.. When either of thelatter two conditions occur, a latch,comprising inverter 183, cathode follower 184, inverter 185 and ,cathode follower 186, is "formed that causes line 228 to go UP. With both lines 228 and 73 UP, AND'circuit 230 is made conductive, operating OR circuit 222 and causinga' positive pulse to be developed by cathode follower 223.-

, Cathode'follower 223 may. also be madeconductive whenever output terminal 74 is UPprovided that line "228 is UP also. Thepositive potentials Ton these lines -op erateAN D circuit 229 and through OR circuit 222 make cathode follower 223'conductive. t, V

The latch, represented by invert'er183, cathode fol- ,loWer 184,. inverter185 and" cathode follower 186,.is controlled further by' inverter226"- in the followin'gm'annet." If either input terminal NR, AGX, srs; input terminals STS and 124A are-UF- simultaneouslfliQR' cit-1 may be operated when output terminal 73 is UP provided that a positive voltage occurs 7 "cuit 225 will befop'erated. Input lines "8T5 "and'124a operate OR circuit 225 through AND circuit 227. Wh en OR circuit 225 is UP, inverter 224 has its output side DOWN and inverter 226 has its output side UP. Thus cathode follower 186 and the latch of which it forms a part may be operated for the purpose of controlling the development of positive pulses on output lines 138, 139, 56 and 57. The logical interrelationship of these circuits of Fig. 12 with the other circuits in the disclosed computing system will be subsequently discussed in conjunction with a timing base developed by the primary pulse distribution chains of Fig. 8.

Fig. 13 illustrates the shift-control circuits that provide pulses particularly for the operation of'the pulse chains of Fig. 10 described above. By selectively applying positive pulses to input terminals 62 and 62A of Fig. 13 it is possible to develop control signals on any one of the output lines a1-a4 and at a corresponding one of the output lines al-agx. It is thus possible to start the accumulator ring of Fig. 10 at any stage'whilethe primary ring of Fig.8 begins at the first stage. In this way any desired relationship of pulses from the primary and accumulator rings may be programmed.

Assuming that an input pulse is applied at input terminal 62A, it may be noted that the top OR circuit and the second from the bottom OR circuit are operated. Operation of the top OR circuit delivers a positive pulse directly to the control'grid of the corresponding circuit that develops an output pulse on line a2. Since, the cathodes of the circuits 116 are connected directly to line 82,' with this line in a negative condition, only circuit 116 that produces the a2 pulse is operated. In the same way, the DOWN condition on line 83 brings about the operation of the circuit associated with output line ag4 to develop a positive pulse on said output line. Inverters 118 produce a positive pulse in'their associated circuits 84 only when there is an absence of a positive pulse on all input lines 62, 62A and 68C. The positive 'pulse'on line 680 serves to develop positive pulses on output lines a4 andiag2. I r

It has been said that select ones of the inverters 84 and 116 are operated whenever lines 82 and 83 are DOWN. This occurs when no positive pulse is applied to OR circuit 81 and whenever cathode followers 202 are not conducting. This condition occurs when a positive pulse is applied on line DGX4 by the primary chain ofFigJ.

8 at the time that line T is UP. Line T is presumed to be UP during the preliminary or pre=operating cycle ,of the primary chain of Fig. 8, as will be subsequently explained. The output of AND circuit 199is UP, the output of double inverter-200 is UP and the positive output of cathode follower 201' along with the-positive A pulse on line BP (see Fig. 2) operates AND circuit 78.; The latter makes inverter 79 conductive which" brings .5

about the de energiza'tion of the latch, comprising double inverter 117 and cathode follower 8t). 7 The negative output developed by cathode follower 80*thereby permits the negative pulse on line NR to be fed to the joined 7 control grids of cathode followers 202, whichplace lines 82 and 83in a DOWN condition." i

Prior'to the development of 'a positive pulse on input A line DGX4, the latch, represented-by inverter 117 and 'cath'o-de' follower 80 is'in an'energized conditionras a i rem-nor a positiveypulse applied on inputline AP. pulse is fed through an OR circuit tothe "control grid of the left triode of double inverter 117-,1'therebydriving cathode follower 80 into-a state of conductivity. Once f this latch is formed, the positive-pulse is continuously I delivered through 'OR circuit 81to cathode followers 202, which maintain" lines 82 and 83 UP un'til the next positive pulse on line DGX4 isgreceived at ofprimarychainoperationf V A h The pulse received from the primary distribution chain I eu egqs z on line DGX4ji also' serves to develop a posit thelend ofleachcycle stepped along at time interval'DG43.

'15 output line 181. This pulse is delivered to the circuit of Fig. 12 where it serves to develop a pulse for reading out information from matrix storage44 of Fig. 1a.

Fig. 14 illustrates the circuits which control operations during multiplication and division. In the case of multiplication input hub 64 is pulsed positively to initiate a multiplication operation. At a time interval determined by a positive condition on input line T, AND circuit 76 is operated and through its associated OR circuit brings about the energization of a latch, comprising double inverter 75 and cathode follower 77. Once this latch is energized at the start of a multiplication operation, it stays in this condition until a negative voltage arrives through inverter 164 at a subsequent time interval, as will be explained later. This latch circuit seres to control the operation of all the control circuits which enter into the multiplication operation.

The positive voltage developed by cathode follower 77 causes output lines 66a and 66b to go UP. The positive voltage on line 66a is fed to the circuit of Fig. 11 where it permits a no carry signal to be developed and a carry signal to be suppressed under certain conditions. The positive voltage on line 66b is delivered to the storage control circuit of Fig. 12, where it serves to develop a positive signal, under certain conditions, for the purpose of transferring the multiplicand from storage unit 44 to adder 49.

The positive voltage developed by cathode follower 77 is also delivered through OR circuit 104 to cathode follower 103 which develops positive voltage on output lines 67a-67d. The positive voltage on line 67a is delivered to the AND circuit 37 of Fig. 8 for the purpose of preventing the stepping along of chain d1-d4 under certain conditions. The positive voltage on line 67b is delivered to the storage control circuit of Fig. 12 Where it serves to control the development of pulses that control the transfer of data from storage unit 44 to adder 49. The positive voltage on line 67c is delivered to AND circuit 105 of Fig. 10 where it serves to reset pulse chains a1-a4 and agl-agx when a positive voltage is developed simultaneously on line AGX. The positive voltage on line 67d is fed to AND circuit 196 of Fig. 11 where it serves to develop a no carry signal and to suppress a carry signal received from adder 49 of Fig. la,- whenever a positive pulse exists simultaneously on input lines D632 and 73a.

At the same time that lines 67 in Fig. 14 are UP, the output line 166 is DOWN. The positive voltage provided by cathode follower 103 makes inverter 168 conductive, thereby preventing cathode follower 169 from operating and output line 166 from going UP Throughout the multiplication operation output line 166 Will be DOWN. This line only goes UP upon the completion of either a multiplication or division operation; inasmuch as the function of the signal on line 166 is to initiate a new operational cycle.

For a division operation, a; positive pulse is applied to input hub 65 of Fig. 141 At a time determined by the presence of a positivevoltage on input line T of Fig. 14, AND circuit 170 is operated and through its associated OR circuit accomplishes the energization of the division control latch made up of double inverter 171, cathode follower 172 and the input OR circuit.

Throughout the division operation, this latch will remain energized and produce a positive voltage for operating the division control circuits. i 1

The'positive voltage developed bycathode follower 72 is made available to output lines 68a-'68c. -The positive voltage on. line 68a is delivered to AND circuit 38 of Fig. 8 where it permits chain group dgx-dg t to be 1 The positive voltage on line 68b is delivered to AND circuit,1 78 of Fig. 12, where it serves to develupapositive pulse on output line 74 fortransferring the complement v lu of the divisor in matrix storage '44 to adder 49. The posi- -age 44 to adder 49 in the 16 tive voltage on output line 68c is delivered through two OR circuits in Fig. 13 to lines 191 and 192 for the purpose of raising UP output lines a4 and ag2.

The positive voltage developed by cathode follower 172 throughout the division operation is also made available through OR circuit 104 and cathode follower 103 to output lines 67a-67d, which perform the functions described above in the case of multiplication. As in multiplication, the positive voltage developed by cathode follower 103 makes inverter 168 conductive and causes cathode follower 169 to bring output line 166 down.

The end of a division operation is sensed by positive pulses occurring simultaneously on lines D632, AG3, A2, 73C, BP and 68E in Fig. 14. This condition operates AND circuit 198 and through an OR circuit makes cathode follower 162 conductive. Output line 71 is thereby caused to go UP, preventing chain group d1-d4 of Fig. 8 from being stepped along.

As soon as cathode follower 162 is made non-conductive, the output of inverter 163 is UP. This causes inverter 164a to bring its output DOWN, thereby terminating the operation of division latch, comprising double inverter 171 and cathode follower 172. The de-energization of this division latch brings DOWN output lines 68a-68c and lines 67a-67d at the same time that it causes output line 166 to go UP.

The de-energization of cathode follower 162 upon the termination of coincidence atthe input ofAND circuit 198 causes the input of inverter 165 to go DOWN and output line 218 to go UP, at the same time that output line 166 goes UP. The positive pulse on line 218 may be fed to a program device (not shown) for the purpose of beginning a new operation cycle.

The circuit of Fig. 14 is also capable of operating switch 53 of Fig. 111 for the purpose of transferring the true or complement value of the number in matrix storfollowing manner. The presence of a positive pulse on line DG2 operates OR circuit 231, causing inverter 176 to go DOWN and thereby preventing cathode follower 177 from conducting.

. mined-by a positive pulse on 70 to go UP. Reference to In this case output line 69 is DOWN and switch 53 is prevented from being operated at a time interval deterline DG11 (Fig. 12). With line 69 DOWN, the output of inverter 174 is UP driving cathode. follower 175 into conduction and making line Fig. 12 will show that when line 70 is UP, line 74 of Fig. 12 is also thereby operating switch 53 of Fig. 1a in a manner to transfer the complement value of the divisor in storage unit 44 to adder 49. So long as output line 70 is UP,- output line 69 will be DOWN because of latch, comprising cathode follower 175, OR circuit 231, inverter 176, cathode follower 177 and inverter 174, formedbypositive pulse on line 70. H

The reverse condition of outputlines 69 and 70 may be realized by the development of coincidence at the input of AND circuit 173. This occurs during the course of a division operation when adder 49 of Fig. 1a develops a no carry signal. With positive voltages on input lines D63, D1, N01, and 68D AND circuit 173 isoperated and through an associate OR circuit makes inverter 174 conductive, and cathode follower Lage unit 44,from.being time when apositivepulse is bemg developed on line 175 non-conductive. This causes output line to go DOWN, thereby preventing the complementary value of the number in storread out into adder 49 at the DGllby the primary'chain of Fig. 8. At'the same L unit 44 tobe transferred by a positive pulse online to prevent the primary 'chain stepped along and, as a result, to develop a changed phase 

